Conditions necessary for the successful initiation and maintenance of type I cell cultures will be studied. Aspects to be considered will include the effect of various substrates, media and serum types and concentrations on attachment, spreading and growth of this cell type. Also selective attachment studies will be pursued as a means of utilizing possible differences in attachment rates by cells other than type I cells. The dye exclusion assay, light microscopic staining techniques and electron microscopy will be used prior to and on successive days following initial cell plating as a means of determining cell identification, viability and plating efficiency. In addition, base DNA, RNA and protein estimates will be made on type I cells first following isolation and enrichment by gradient sedimentation and at various times following cell plating.